It has long been recognized in the art that there is a need to detect parameters which indicate the possibility of the tire failure and also to detect various other parameters which can be used in various vehicular control systems. As an example, the detection of temperature, pressure, and deflation of a tire can indicate that a failure of the tire is pending and, thus, the avoidance of a potentially hazardous or even fatal situation is made possible.
The present invention is also useful in providing signals for various automatic systems frequently used in vehicles. As is known, such parameters as the rotational speed of the tire and the acceleration of the tire are used in automatic speed control systems and in automatic breaking (antiskid) systems respectively. The inventive system can be used to obtain both these signals.
The need for devices which will yield output signals in response to hazardous conditions, such as deflation, has long been recognized in the art, as is evidenced by such patents as U.S. Pat. No. 4,117,452. This patent is exemplary of prior art devices which are utilized to detect the sudden deflation of the tire and to yield an output signal in response to such deflation. This patent also is exemplary of the deficiencies of the prior art because it is limited to the detection of deflation only and does not suggest responsiveness to elevated temperatures and does not suggest a technique for providing a biasing signal to a transmitter and its accompanying circuitry which are totally enclosed within the tire. The various devices presently found in the art are deficient and of very limited utility because they require wires, or other connecting means, running into and out of the tire in order to provide the biasing voltages to the system within the tire and to transport the output signal outside the tire. Also, the rotation of the tire during travel causes severe problems in coupling the transmitter to the biasing voltage source and also to the receiving apparatus which is utilized to receive the fault signal.
The prior art available thus is deficient in that it is void a teaching of a mechanism for providing the required regulated biasing voltages to the transmitters and other electrical apparatus which are contained within the tire. Thus, the prior art devices are responsive to a particular fault but are not useful with transducers which are intentionally placed and arranged to measure predetermined parameters of the tire such as speed, pressure, temperature, fatigue, etc. The prior art is also deficient because it does not show or suggest a system which can be used to transmit detected parameters, such as speed and acceleration.